A typical appliance, such as a refrigerator-freezer, uses a damper assembly to control the movement of air from the freezer to a fresh food compartment to control the temperature of the fresh food compartment. While there exists several types of passive and manually actuated damper assemblies, many damper assemblies use one of the various types of alternating-current, synchronous motors (hereinafter “AC motor”), such as a single-direction AC motor or a bi-directional AC motor, to drive the damper door within the damper assembly between its open and closed positions.
A first type of motor driven damper assembly, known as a “door style” damper assembly, uses a single-direction AC motor to drive a damper door from a closed position to an open position. Because the door style damper assembly only employs a single-direction AC motor, the damper assembly must rely on a spring or other means to draw a damper door back and return the damper assembly to the closed position.
A second type of damper assembly, known as a “rotary” damper assembly, also typically uses a single-direction AC motor to drive or rotate the damper door in the damper assembly between the closed position and the open position. However, the rotary damper assembly works quite differently from the door style damper assembly. The typical rotary damper assembly includes inner and outer hollow cylinders, each having one or more apertures through which fluid may flow. These apertures may be axial or radial, or both. The inner cylinder is nested within the outer cylinder in a manner that permits relative axial rotation of the cylinders about a common longitudinal axis. In axial type rotary dampers assemblies, this inner cylinder receives the fluid flow at an axial inlet. In radial type rotary damper assemblies, the fluid flow enters through a radial inlet in the side wall of both the inner and outer cylinders. The flow of fluid out of the assembly is typically in a radial direction through the side wall apertures, and may also be via an axial aperture. The size of the opening formed by the side wall apertures is proportional to the degree of alignment of the cylinder apertures.
One such rotary damper system is disclosed in U.S. Pat. No. 6,240,735, to Kolson, et al., entitled ROTARY DAMPER ASSEMBLY, and assigned to the assignee of the instant application, the teachings and disclosure of which are hereby incorporated in their entireties by reference thereto. Another is disclosed in U.S. patent application Ser. No. 10/620,104, to Pearson, et al., entitled FLOW-THROUGH ROTARY DAMPER PROVIDING COMPARTMENT SELECTIVITY FOR A MULTI-COMPARTMENT REFRIGERATOR, and assigned to the assignee of the instant application, the teachings and disclosure of which are hereby incorporated in their entireties by reference thereto.
These damper assemblies can first be placed in the closed position by activating the single-direction AC motor until the inner cylinder in the damper is rotated until the two (or more) openings of the inner and outer cylinders are not in alignment. Alternatively, when the damper assembly is to be placed in the open position, the single-direction AC motor is again activated and continues to drive the inner cylinder in the same direction as before until the openings in the two cylinders are aligned. The downfall of such a rotary damper assembly is that, unless there is an extremely tight tolerance between the inner and outer cylinders, air will leak between them even when the damper assembly is rotated to its closed position.
To minimize such leakage, some rotary damper assemblies include a sealing flange or like structure between the two cylinders. Such a structure is meant to provide a barrier to fluid flow when the damper assembly is in the closed position. However, unless there is an extremely tight tolerance between the cylinder and the flange, air will leak even when the damper assembly is rotated to its closed position. This is because there is a lack of positive engagement between the inner cylinder or its “damper” and the sealing flange. As a result, air is still permitted to undesirably flow.
This problem is overcome in a third type of damper assembly, known as a “bi-directional” damper assembly. In such a damper assembly, a motor that can rotate in more than a single-direction, such as a bi-directional AC motor, a direct current motor, or a stepper motor, is used. The bi-directional damper assembly is capable of driving a damper door or a drum in the damper assembly in two different directions, such as forward and reverse. Therefore, when the damper assembly is to be closed, the bi-directional motor drives the damper door forward until the damper door positively engages with a sealing flange. This positive engagement prevents leakage of fluid through the damper assembly in the closed position. Thereafter, when the damper door is to be opened, the damper assembly drives the damper door in the opposite direction. While positive engagement between the damper and the sealing flange is desirable to prevent the fluid leakage in the closed position discussed above, bi-directional motors used to achieve this result are costly. Therefore, damper assemblies that use these bi-directional motors are extremely expensive. As such, they are typically only used in top of the line appliance models.
There exists, therefore, a need in the art for an inexpensive rotary damper assembly that provides a positive contact force closure of the damper door to prevent or minimize any fluid leakage through the damper door in its closed position.